Template assembly and method of producing template assembly

ABSTRACT

The invention is directed to a template assembly configured to hold a workpiece in polishing of the workpiece, including: a PET base; an annular template adhering to an outer circumferential portion of a lower surface of the PET base, the template having an annular notch formed at an upper portion of an inner surface of the template; and a discoid backing pad whose peripheral portion is fitted into the notch, the backing pad adhering to a central portion of the lower surface of the PET base, wherein a recess configured to receive and hold the workpiece during polishing is defined by the inner surface of the template and a lower surface of the backing pad. This template assembly can reduce in-plane variation in depth of the recess and thereby improve flatness of a polished workpiece while inhibiting the occurrence of a scratch and a defect of the workpiece.

TECHNICAL FIELD

The present invention relates to a template assembly used in polishingof a surface of workpieces, such as various semiconductor wafersstarting with silicon wafers, to hold the workpiece and a method ofproducing the template assembly.

BACKGROUND ART

The apparatuses that can be mentioned as apparatuses for polishingsurfaces of a workpiece such as a silicon wafer are a single-sidepolishing apparatus to polish one surface of the workpiece at a time anda double-side polishing apparatus to polish both surfaces of theworkpiece simultaneously. A typical single-side polishing apparatus 200as shown in FIG. 8 is constituted of a turn table 203 to which apolishing pad 202 is attached, a polishing agent supply mechanism 204, apolishing head 201, and so on. The polishing apparatus 200 holds aworkpiece W with the polishing head 201, rotates the turn table 203 andthe polishing head 201 while supplying a polishing agent 205 to thepolishing pad 202 from the polishing agent supply mechanism 204, andbrings a surface of the workpiece W into sliding contact with thepolishing pad 202 to polish the workpiece W.

A polishing head with a retainer ring or a polishing head with atemplate assembly is used as a means of holding a workpiece.

This polishing head with a retainer ring serves a function to press apolishing pad at the periphery of the workpiece by the retainer ring andthereby to prevent compressive deformation of the polishing pad due tothe workpiece itself, so as to prevent an outer peripheral sag of theworkpiece. The structure of this polishing head however is complicatedand makes its cost high.

FIG. 9 shows an example of a conventional polishing head with a templateassembly. As shown in FIG. 9, this template assembly has a backing pad102 and an annular template 103 adhering to the outer circumferentialportion of the lower surface of the backing pad. The inner surface ofthe template and the lower surface of the backing pad 102 define arecess. During polishing, a workpiece W is received and held in thisrecess. The polishing head 101 is configured such that this templateassembly is stuck to a polishing head body 104 by double-stick tape 105.Glass epoxy resin, for example, is used as the material of the template103.

In this polishing head 101 with the template assembly, the shape of theouter circumference of the wafer W is controlled by a difference betweenthe depth of the recess of the template assembly and the thickness ofthe wafer W. In other words, proper selection of the thickness of thetemplate 103 enables adjustment of the pressure of the workpiece outercircumference during polishing, so the outer peripheral sag can becomparatively readily inhibited without using a polishing head having acomplicated structure.

However, variation in the depth of the recess of the template assemblyis larger compared with the precision of the thickness of a wafer. Thismakes it difficult to stably achieve the target difference in thethickness.

Accordingly, the surface of the backing pad is subjected to a buffingprocess after the backing pad is formed or the template is ground orlapped to improve the variation in the depth of the recess (See PatentDocument 1).

A template assembly with a PET base, as shown in FIG. 10, is also known(See Patent Document 2). As shown in FIG. 10, in the template assembly110, a template 103 subjected to a grinding or lapping process is stuckdirectly to a PET base 106 and a backing pad 102 having a thicknesswhose variation is reduced by a buffing process is attached to theinside of the template.

CITATION LIST Patent Literature

-   Patent Document 1: Japanese Unexamined Patent publication (Kokai)    No. 2009-208199-   Patent Document 2: Japanese Unexamined Patent publication (Kokai)    No. 2008-93811-   Patent Document 3: Japanese Unexamined Patent publication (Kokai)    No. H7-58066

SUMMARY OF INVENTION Technical Problem

The above method of buffing the backing pad or grinding and polishingthe template is effective in reducing variation in thickness of each ofthe backing pad and the template. It is however difficult to improve theprecision of adhesion between the template and the backing pad, which isan elastic body. The precision of the template assembly such as in-planevariation in depth of the recess cannot greatly be improved.

The recess of a commercially available template assembly has the depthwith precision of a variation of ±20 μm from the target value. In-planevariation of the depth is about 15 μm.

Variation in thickness from the target thickness of the template can beimproved to within ±3 μm and in-plane variation in its thickness can beimproved to 3 μm or less after grinding and polishing the template.After the template is stuck to the backing pad, however, the recess ofthe template assembly has the depth with precision of a variation of ±10μm from the target value and the in-plane variation in the depth isdegraded to about 10 μm.

In the template assembly 110 shown in FIG. 10, which has the templateand the backing pad directly stuck to the PET base, the precision ofadhesion can comparatively readily be improved because glass epoxy resinused as the template is hard, so the precision of the template assemblycan be improved. Since the backing pad having a discoid shape isattached to the inner surface of the template, however, a space iscreated between the template and the backing pad. During polishing,slurry enters this space. This slurry is a source of generatingparticles that exerts an adverse effect on the quality of a polishedworkpiece such as a fine scratch and a defect of the workpiece.

Compared with the template assembly having the template stuck to thebacking pad as shown in FIG. 9, the template assembly 110 having thetemplate with an increased thickness has a smaller gap between thetemplate and the polishing pad because the template hardly sinks induring polishing. This results in a shortage of slurry supply to aworkpiece surface and may adversely affect the workpiece quality.Accordingly, the template cannot be thickened too much.

It is also known that an annular groove is formed in the backing padalong the inner surface of the template so that the outer peripheral sagof a workpiece is inhibited (See Patent Document 3). Even this methodcannot improve defects on the workpiece surface because the slurryenters the groove during polishing and becomes the source of generatingparticles.

The present invention was accomplished in view of the above-describedproblems. It is an object of the present invention to provide a templateassembly that can reduce the in-plane variation in depth of the recessand thereby improve flatness of a polished workpiece while inhibitingthe occurrence of a scratch and a defect of the workpiece.

Solution to Problem

To achieve this object, the present invention provides a templateassembly configured to hold a workpiece in polishing of the workpiece,comprising: a polyethylene terephthalate (PET) base; an annular templateadhering to an outer circumferential portion of a lower surface of thePET base, the template having an annular notch formed at an upperportion of an inner surface of the template; and a discoid backing padwhose peripheral portion is fitted into the notch, the backing padadhering to a central portion of the lower surface of the PET base,wherein a recess configured to receive and hold the workpiece duringpolishing is defined by the inner surface of the template and a lowersurface of the backing pad.

Such a template assembly has no space between the template and thebacking pad and generate no particle during polishing, thereby enablinginhibition of the occurrence of the scratch and defect of the workpiece.In addition, since the template and the backing pad are stuck to the PETbase, this template assembly can reduce in-plane variation in theirthickness and hence in-plane variation in depth of the recess andthereby improve the flatness of the polished workpiece.

The notch preferably has a thickness equal to or less than a targetthickness of the backing pad.

Such a template assembly prevents the formation of a space between thetemplate and the backing pad. If the notch has a thickness less than thetarget thickness of the backing pad, then a polishing pressure of theouter circumferential portion of the workpiece can be reduced and theamount of polishing the outer circumferential portion of the workpiececan thereby be reduced, so the outer peripheral sag can be inhibited.

The template is preferably made of glass epoxy resin.

Such a template has excellent mechanical properties and can preventmetal contamination and scratch of the workpiece.

Moreover, in-plane variation in depth of the recess is preferably equalto or less than 10 μm.

Such a template assembly can reliably improve the flatness of thepolished workpiece.

Furthermore, the present invention provides a method of producing theinventive template assembly, comprising: preparing the annular templatehaving the annular notch formed at the upper portion of the innersurface of the template; sticking the discoid backing pad on the centralportion of the PET base; and sticking the template on the outercircumferential portion of the lower surface of the PET base such thatthe peripheral portion of the backing pad is fitted into the notch ofthe template.

This method can produce the inventive template assembly that can reducethe in-plane variation in the thickness of the template and the backingpad and improve the flatness of the polished workpiece while inhibitingthe occurrence of the scratch and defect of the workpiece.

The step of preparing the template may include: preparing a substratefor the template; cutting the prepared substrate into an annular shape;and then forming the notch by grinding an upper portion of an innersurface of the annular substrate.

In this manner, the annular template having the notch can readily beprepared.

The step of preparing the template preferably includes: before formingthe notch, lapping and/or polishing the template such that in-planevariation in thickness of the template is equal to or less than 10 μm.

In this manner, the in-plane variation in depth of the recess that isdefined by the inner surface of the template and the lower surface ofthe backing pad can reliably be reduced.

Advantageous Effects of Invention

The inventive template assembly includes a PET base, an annular templateadhering to the outer circumferential portion of the lower surface ofthe PET base, and a discoid backing pad adhering to the central portionof the lower surface of the PET base; an annular notch is formed at anupper portion of the inner surface of the template; a peripheral portionof the backing pad is fitted into the notch. This template assembly caninhibit the occurrence of the scratch and defect of a workpiece withoutgenerating particles during polishing, and reduce the in-plane variationin thickness of the template and the backing pad and hence the in-planevariation in depth of the recess, thereby enabling improvement inflatness of a polished workpiece.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an example of the inventive templateassembly;

FIG. 2 is an enlarged view around the notch having the same thickness asthe target thickness of the backing pad of the inventive templateassembly;

FIG. 3 is an enlarged view around the notch having a smaller thicknessthan the target thickness of the backing pad of the inventive templateassembly;

FIG. 4 is a diagram of the relationship of roll off to variation indepth of the recess from the target value in examples 1 and 2 andcomparative examples 1 and 2;

FIG. 5 is a diagram showing the average, the maximum, and the minimum ofroll off in examples 1 and 2 and comparative examples 1 and 2;

FIG. 6 is a radar chart of a difference in position of roll off at eightpoints in a plane in examples 1 and 2 and comparative examples 1 and 2;

FIG. 7 is a diagram showing the number of defects of wafers in examples1 and 2 and comparative examples 1 and 3;

FIG. 8 is a schematic diagram of an example of a common polishingapparatus;

FIG. 9 is a schematic diagram of an example of a conventional templateassembly;

FIG. 10 is a schematic diagram of another example of a conventionaltemplate assembly; and

FIG. 11 is an explanatory view of a method of measuring the depth of therecess in examples 1 and 2 and comparative examples 1 to 3.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be hereinafter described,but the present invention is not limited to this embodiment.

First, the inventive template assembly will be described with referenceto FIGS. 1 and 2.

As shown in FIG. 1, the inventive template assembly 1 has a polyethyleneterephthalate (PET) base 2, an annular template 3, and a discoid backingpad 4. The thickness and the shape of the PET base 2 are notparticularly limited; for example, the shape may be discoid.

The backing pad 4 holds a workpiece W by attaching the workpiece W onits lower surface containing water. The backing pad 4 may be made of,for example, foamed polyurethane. This backing pad 4 containing watercan reliably hold the workpiece W by surface tension of the wafercontained in the backing pad 4.

The template 3 is stuck on an outer circumferential portion of the lowersurface of the PET base 2. The backing pad 4 is stuck on a centralportion of the lower surface of the PET base 2.

The inner surface of the template 3 and the lower surface of the backingpad 4 define a recess 6. During polishing of the workpiece W, theworkpiece W is received in this recess 6, and the edge and the uppersurface of the workpiece W are held on the inner surface of the template3 and the lower surface of the backing pad 4, respectively.

The template assembly having the template 3 and backing pad 4 that bothadhere directly to the PET base 2 in this manner can reduce thedifference between the actual depth and the target depth of the recess 6and the in-plane variation of the depth of the recess 6. Accordingly,the flatness of the workpiece W polished with the inventive templateassembly can be improved especially by reducing the outer peripheral sagof the workpiece W. In particular, when the in-plane variation in depthof the recess is 10 μm or less, the flatness of the workpiece W canreliably be improved.

The template 3 is preferably made of a material that is softer than theworkpiece W and has high abrasion resistance that makes it hard to wearwhen being brought into sliding contact with a polishing pad duringpolishing, for such a material avoids contamination, a scratch, and animpression of the workpiece W. From this viewpoint, an exemplarymaterial of the template 3 may be glass epoxy resin.

As shown in FIG. 1, an annular notch 5 is formed at an upper portion ofthe inner surface of the template 3. The backing pad 4 is stuck on thecentral portion of the lower surface of the PET base 2 such that aperipheral portion of the backing pad 4 is fitted into the notch 5. Thisconfiguration allows the template assembly to use the template 3 and thebacking pad 4 that are directly stuck on the PET base 2 and have nospace between the template 3 and the backing pad 4. This templateassembly can thereby prevent the generation of particles due to slurryentering a space during polishing and inhibit the occurrence of a finescratch and defect of the workpiece, which are problems of aconventional template assembly.

As shown in FIG. 2, the notch 5 preferably has a thickness d that isequal to or less than the target thickness of the backing pad 4 so thatno space is defined between the backing pad 4 and the template.

As shown in FIG. 3, the notch 5 may have a thickness d less than thetarget thickness of the backing pad 4 so that the outer peripheral sagof the workpiece is more effectively inhibited. In this manner, theperipheral portion of the backing pad 4 that is held by the template 3is compressed annularly, resulting in reduction in polishing pressure ofthe outer circumferential portion of the workpiece. This reductionreduces the amount of polishing the outer circumferential portion of theworkpiece and thereby enables the inhibition of the outer peripheral sagof the workpiece.

The inventive template assembly with the notch 5 can adjust thepolishing pressure of the outer circumferential portion of the workpieceby adjusting the thickness of the notch 5 without changing the thicknessof the template 3. The template assembly can therefore inhibit ashortage of slurry supply due to a decreased space between the template3 and the polishing pad, thereby enabling the inhibition of theoccurrence of surface defects of the workpiece.

This configuration also allows for the combination with the method offorming an annular groove in the backing pad 4.

Next, the method of producing the inventive template assembly will bedescribed.

As shown in FIG. 1, the annular template 3 having the annular notch 5formed at the upper portion of its inner surface is first prepared. Thisstep may be performed for example as follows:

A substrate for the template such as a glass epoxy resin substrate isprepared. This substrate is lapped and/or polished so as to have thetarget thickness.

At this time, the in-plane variation in thickness of the template 3 ispreferably reduced to 10 μm or less. In this manner, the surface shapeof the outer circumferential portion of the workpiece can be inhibitedfrom partially degrading during polishing of the workpiece.

If lapping is performed at this time, then exemplary abrasive grainsthat can be used are alumina or SiC abrasive grains. If polishing isperformed at this time, then an alkali solution containing colloidalsilica, for example, can be used.

The substrate is then cleaned to remove the abrasive grains and/oralkali solution attached in the lapping and/or polishing.

The substrate is next cut into the annular template 3, for example, by anumerical control. The notch 5 is then formed by grinding the upperportion of the inner surface of the annular template 3. In thisgrinding, the thickness of the notch 5 is adjusted to a prescribedthickness that is equal to or less than the target thickness of thebacking pad 4, as described above.

The discoid backing pad 4 is stuck on the central portion of the PETbase 2. The diameter of the backing pad 4 is adjusted such that thebacking pad can be fitted into the annular notch 5 formed as above. Thetemplate 3 is stuck on the outer circumferential portion of the lowersurface of the PET base 2 such that the peripheral portion of thebacking pad 4 is fitted into the notch 5 of the template 3.

This inventive method can produce the inventive template assembly.

EXAMPLE

The present invention will be more specifically described with referenceto examples and comparative examples, but the present invention is notlimited to these examples.

Example 1

The inventive template assembly as shown in FIG. 1 was producedaccording to the inventive producing method to evaluate the precision ofthe depth of the recess. The precision of the depth of the recess wasevaluated by the difference in depth from the target depth and thein-plane variation in depth.

A glass epoxy resin substrate was lapped so as to have a thickness closeto the target thickness. The substrate was then polished with a slurrycontaining about 1 μm of cerium oxide powder and cut into an annularshape with a prescribed size. The notch having the same thickness as thebacking pad was then formed by annularly grinding the substrate up to aposition of 5 mm away from the inner circumference with a lathe.

The template thus produced was stuck to the PET base on which thebacking pad was stuck on its central portion to complete the productionof the template assembly.

The depth of the recess of this template assembly was measured. As shownin Table 1, the difference from the target depth was an average (Ave) of−0.51 μm, and a maximum of 4.8 μm on the plus side (Max) and 6.5 μm onthe minus side (Min). As shown in Table 2, the in-plane variation indepth was an average (Ave) of 5.3 μm and a maximum (Max) of 7 μm interms of the range of eight measurement points. It was revealed fromthese results that the precision of the depth of the recess was greatlyimproved compared with the results in comparative examples 1 and 2 asdescribed later.

At that time, the depth of the recess was measured in the followingmanner. As shown in FIG. 11, the workpiece was marked at eight points inits plane within 1 to 2 mm away from its outer circumference. Thethickness of the marked portions was measured (this measured thicknessis referred to as workpiece thickness). This workpiece was put into therecess of the template assembly. The thickness of the marked portions ofthe workpiece was measured while a load of 100 g/cm² was applied to theworkpiece (this measured thickness is referred to as workpiece-portionthickness). The thickness of the template was also measured at aposition of 1 to 2 mm away from the inner circumference of the templatetoward the outer circumference (this measured thickness is referred toas template thickness). These measured values were used to calculate thedepth of the recess by using the following expression. The average ofthe eight points and its range were used as the central value of therecess depth.

Recess depth=template thickness−(workpiece-portion thickness−workpiecethickness)

These thicknesses were measured with a height gage HDF-300N made byMitutoyo Corp.

Then, 300-mm-diameter silicon wafers were polished with a polishingapparatus, as shown in FIG. 8, having the template assembly produced inexample 1 to evaluate flatness and surface defects of the wafers. Theflatness was evaluated by roll off measurement with an edge roll offmeasuring system LER-310M made by Kobelco Research Institute.

The portion of 3 to 6 mm away from the outer circumference was regardedas a reference surface to calculate the value of roll off. The roll offwas measured on four wafers at 0.5 mm, 0.7 mm, 1.0 mm, and 2.0 mm awayfrom their outer circumference.

Table 3 shows the average of roll off values at these points. Table 4shows the relationship between the difference in the recess depth fromthe target depth shown in Table 1 and the roll off shown in Table 3. Asshown in FIG. 4, the difference in the recess depth from the targetdepth was a minus value (the recess depth was shallower). As theabsolute value of this difference increased, the template was moredifficult to reduce the polishing pressure of the outer circumferentialportion of the workpiece. In particular, the roll off was significantlychanged at 0.5 mm away from the outer circumference, which is easy to beaffected by the recess depth.

FIG. 5 shows the average (Ave), the maximum (Max), and the minimum (Min)of the roll off at 0.5 mm away from the outer circumference of eachwafer. FIG. 6 shows radar charts that demonstrate how the positions ofthe roll off were changed at the measured eight points in the plane.

As shown in FIGS. 5 and 6, example 1 carried out a further improvementin the roll off and a greater improvement in the in-plane variationcompared with comparative examples 1 and 2 as described later, becauseexample 1 achieved substantially the same recess depth as the targetdepth.

In addition, as shown in FIG. 6, the radar chart exhibits substantiallyconcentric circles, which means that the in-plane variation in the rolloff was inhibited.

FIG. 7 shows the result of the surface defects of the wafers. As shownin FIG. 7, the occurrence of the surface defects of the wafers wasinhibited compared with the result in comparative example 3 as describedlater.

The surface defects were evaluated with Magics 350 made by LasertecCorporation as values converted such that the total number of defects incomparative example 1 was regarded as 1.0.

Example 2

The inventive template assembly was produced in the same manner asexample 1 except that the thickness of the template was 10 μm thinnerthan the thickness in example 1 and the thickness of the notch was 20 μmthinner than the thickness of the backing pad. The same evaluation asexample 1 was conducted. It is to be noted that the thickness of thisnotch was adjusted such that although the used template was 10 μmthinner than the thickness in example 1, the depth of the recess when aload of 100 g/cm² was applied to the workpiece became substantially thesame as in example 1 by pressing the peripheral portion of the backingpad with the template.

The depth of the recess of this template assembly was measured. As shownin Table 1, the difference from the target depth was an average of −0.43μm, and a maximum of 2.0 μm on the plus side and 2.8 μm on the minusside. As shown in Table 2, the in-plane variation in depth was anaverage of 5.8 μm and a maximum of 7 μm in terms of the range of eightmeasurement points. It was revealed from these results that theprecision of the depth of the recess was greatly improved compared withthe results in comparative examples 1 and 2 as described later.

Then, 300-mm-diameter silicon wafers were polished with a polishingapparatus, as shown in FIG. 8, having the template assembly produced inexample 2 to evaluate flatness and surface defects of the wafers as inexample 1.

Although example 2 used the template having the different thickness fromthe thickness in example 1 as above, since the recess depth wassubstantially the same as example 1, the same result of the roll off ofthe polished wafers was obtained. It was revealed from the radar chartshown in FIG. 6 that the in-plane variation in roll off was inhibited asin example 1.

FIG. 7 shows the result of the surface defects of the wafers. As shownin FIG. 7, the occurrence of the surface defects of the wafers wasinhibited compared with the result in comparative example 3 as describedlater.

The roll off values of the polished wafers in examples 1 and 2 were onthe same level. The in-plane variations of the roll off were also on thesame level. More specifically, even when the template is thinned likeexample 2, the recess having the target depth can be formed by adjustingthe thickness of the notch. This allows the template to have a thinnerthickness than the conventionally required thickness, even when a deeprecess, which may reduce slurry supply to the wafer surface duringpolishing, is chosen, for example, in consideration for the effect ofthe compressibility of a polishing pad to be used. The roll off and thesurface defects of the wafers can thereby be improved while thereduction in slurry supply to the workpiece surface is inhibited duringpolishing.

Comparative Example 1

The same evaluation as example 1 was conducted by using a conventionaltemplate assembly, which is commercially available, having a templatestuck on the outer circumferential portion of the lower surface of abaking pad as shown in FIG. 9 without performing lapping and polishingon the template.

The depth of the recess of this template assembly was measured. As shownin Table 1, the difference from the target depth was an average of −4.46μm, and a maximum of 11.0 μm on the plus side and 16.9 μm on the minusside. As shown in Table 2, the in-plane variation in depth was anaverage of 15.63 μm and a maximum of 26 μm in terms of the range ofeight measurement points. It was revealed from these results that theprecision of the depth of the recess was considerably worse comparedwith the results in examples 1 and 2.

Then, 300-mm-diameter silicon wafers were polished with a polishingapparatus, as shown in FIG. 8, having the template assembly incomparative example 1 to conduct the same evaluation as example 1.

As shown in Tables 1 and 2, since the difference in the recess depthfrom the target depth in comparative example 1 was larger than those inexamples 1 and 2, the roll off and the in-plane variation were alsolarger. It was revealed from the radar chart shown in FIG. 6 that somewafers had a deviation in roll off in its plane.

FIG. 7 shows the result of the surface defects of the wafers. As shownin FIG. 7, since the template assembly used in comparative example 1 hadno space between the template and the backing pad unlike FIG. 10, theoccurrence of the surface defects of the wafers was inhibited comparedwith comparative example 3.

Comparative Example 2

The same evaluation as comparative example 1 was conducted by using thesame template assembly as comparative example 1 except that the templatewas lapped.

The depth of the recess of this template assembly was measured. As shownin Table 1, the difference from the target depth was an average of −3.04μm, and a maximum of 8.9 μm on the plus side and 10.9 μm on the minusside. As shown in Table 2, the in-plane variation in depth was anaverage of 9.77 μm and a maximum of 16 μm in terms of the range of eightmeasurement points.

It was revealed that although the precision of depth of the recess wasimproved by performing lapping on the template compared with comparativeexample 1, this precision of depth was considerably worse compared withthe results in examples 1 and 2.

Then, 300-mm-diameter silicon wafers were polished with a polishingapparatus, as shown in FIG. 8, having the template assembly incomparative example 2 to evaluate the flatness as in example 1.

As shown in Tables 1 and 2, since the difference in the recess depthfrom the target depth in comparative example 2 was smaller than that incomparative example 1, the roll off and in-plane variation were improvedcompared with comparative example 1, but significantly worse than thosein examples 1 and 2. It was revealed from the radar chart shown in FIG.6 that some wafers had a deviation in roll off in its plane likecomparative example 1 and the variation in the roll off at the outercircumference was not inhibited.

Since the difference in the recess depth from the target depth can bereduced by an adjustment of the thickness of components to be used or animprovement of sticking method, the average of roll off can be improvedto some degree as demonstrated in comparative example 2. The in-planevariation in roll off, however, cannot be improved. In contrast, theinventive template assembly can also improve this in-plane variation asabove.

Table 1 shows summarized results of the difference in the recess depthfrom the target depth in examples 1 and 2 and comparative examples 1 and2. Table 2 shows summarized results of the in-plane variation in therecess depth in examples 1 and 2 and comparative examples 1 and 2.

TABLE 1 COMPARATIVE COMPARATIVE EXAMPLE EXAMPLE EXAMPLE 1 EXAMPLE 2 1 2N 40 26 10 5 Ave −4.46 −3.04 −0.51 −0.43 S 7.37 6.00 3.53 2.03 Max 11.08.9 4.8 2.0 Min −16.9 −10.9 −6.5 −2.8

TABLE 2 COMPARATIVE COMPARATIVE EXAMPLE 1 EXAMPLE 2 EXAMPLE 1 EXAMPLE 2N 40 26 10 5 Ave 15.63 9.77 5.30 5.80 S 4.91 2.67 1.64 1.30 Max 26.016.0 7.0 7.0 Min 8.0 6.0 2.0 4.0

TABLE 3 DIFFERENCE IN RECESS DEPTH FROM ROLL OFF TARGET DEPTH 0.5 mm 0.7mm 1.0 mm 2.0 mm comparative −4.46 0.27 0.10 0.05 0.01 example 1comparative −3.04 0.23 0.08 0.04 0.01 example 2 example 1 −0.51 0.130.07 0.03 0.00 example 2 −0.43 0.12 0.08 0.03 0.00

Comparative Example 3

With a polishing apparatus, as shown in FIG. 8, having a conventionaltemplate assembly with a template having no notch as shown in FIG. 10,300-mm-diameter silicon wafers were polished to evaluate the in-planevariation in the recess depth and surface defects of the wafers as inexample 1.

The result was that although the same level of the in-plane variation inthe recess depth as examples 1 and 2 was obtained, the surface defectsof the wafers were degraded compared with examples 1 and 2 andcomparative example 1. It can be understood that these surface defectswere due to particles generated by slurry entering the space between thetemplate and the backing pad during polishing.

It is to be noted that the present invention is not limited to theforegoing embodiment. The embodiment is just an exemplification, and anyexamples that have substantially the same feature and demonstrate thesame functions and effects as those in the technical concept describedin claims of the present invention are included in the technical scopeof the present invention.

1-7. (canceled)
 8. A template assembly configured to hold a workpiece inpolishing of the workpiece, comprising: a polyethylene terephthalate(PET) base; an annular template adhering to an outer circumferentialportion of a lower surface of the PET base, the template having anannular notch formed at an upper portion of an inner surface of thetemplate; and a discoid backing pad whose a peripheral portion is fittedinto the notch, the backing pad adhering to a central portion of thelower surface of the PET base, wherein a recess configured to receiveand hold the workpiece during polishing is defined by the inner surfaceof the template and a lower surface of the backing pad.
 9. The templateassembly according to claim 8, wherein the notch has a thickness equalto or less than a target thickness of the backing pad.
 10. The templateassembly according to claim 8, wherein the template is made of glassepoxy resin.
 11. The template assembly according to claim 9, wherein thetemplate is made of glass epoxy resin.
 12. The template assemblyaccording to claim 8, wherein in-plane variation in depth of the recessis equal to or less than 10 μm.
 13. The template assembly according toclaim 9, wherein in-plane variation in depth of the recess is equal toor less than 10 μm.
 14. The template assembly according to claim 10,wherein in-plane variation in depth of the recess is equal to or lessthan 10 μm.
 15. The template assembly according to claim 11, whereinin-plane variation in depth of the recess is equal to or less than 10μm.
 16. A method of producing a template assembly according to claim 8,comprising: preparing the annular template having the annular notchformed at the upper portion of the inner surface of the template;sticking the discoid backing pad on the central portion of the PET base;and sticking the template on the outer circumferential portion of thelower surface of the PET base such that the peripheral portion of thebacking pad is fitted into the notch of the template.
 17. A method ofproducing a template assembly according to claim 15, comprising:preparing the annular template having the annular notch formed at theupper portion of the inner surface of the template; sticking the discoidbacking pad on the central portion of the PET base; and sticking thetemplate on the outer circumferential portion of the lower surface ofthe PET base such that the peripheral portion of the backing pad isfitted into the notch of the template.
 18. The method according to claim16, wherein the step of preparing the template includes: preparing asubstrate for the template; cutting the prepared substrate into anannular shape; and then forming the notch by grinding an upper portionof an inner surface of the annular substrate.
 19. The method accordingto claim 17, wherein the step of preparing the template includes:preparing a substrate for the template; cutting the prepared substrateinto an annular shape; and then forming the notch by grinding an upperportion of an inner surface of the annular substrate.
 20. The methodaccording to claim 16, wherein the step of preparing the templateincludes: before forming the notch, lapping and/or polishing thetemplate such that in-plane variation in thickness of the template isequal to or less than 10 μm.
 21. The method according to claim 17,wherein the step of preparing the template includes: before forming thenotch, lapping and/or polishing the template such that in-planevariation in thickness of the template is equal to or less than 10 μm.22. The method according to claim 18, wherein the step of preparing thetemplate includes: before forming the notch, lapping and/or polishingthe template such that in-plane variation in thickness of the templateis equal to or less than 10 μm.
 23. The method according to claim 19,wherein the step of preparing the template includes: before forming thenotch, lapping and/or polishing the template such that in-planevariation in thickness of the template is equal to or less than 10 μm.